Shower base



FIG. 1 is a top perspective view of a shower base embodying my new design;

FIG. 2 is a rear plan view thereof;

FIG. 3 is a front plan view thereof;

FIG. 4 is a left side plan view thereof;

FIG. 5 is a right side plan view thereof; and

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof. 

CLAIM The ornamental design for a shower base, as shown and described. 